Transparent thermoplastic sheet, especially polycarbonate sheet, is used in a wide number of applications requiring impact strength and transparency. A number of these applications utilize the impact strength of transparent thermoplastic sheet to render an object both available for view yet protected from tampering or theft and the like. Such applications include picture frames, display windows, protective covers for stained glass, and the like. These applications have in common a need to clearly view the object being protected while rendering the object inaccessible to the viewer. However, it has long been a problem that transparent thermoplastic sheet reflects a substantial portion of the light incident on its surface and thus has a problem with glare. In many situations, especially outdoor situations, the glare caused by such reflection renders the protected object unviewable.
U.S. Pat. Nos. 4,399,192 and 4,407,855, Russell, disclose a radiation curable polyfunctional acrylate composition for use as a mar resistant coating for inter alia polycarbonate substrates. Flatting agents may be added to the coating composition and a polycarbonate sheet coated with such is recommended for use as a low reflection filter for cathode ray tubes.
It is known that transparent thermoplastic sheet or film may be textured on one surface and coated with an acrylic protective coat to provide a transparent low glare thermoplastic sheet. However, such sheet as made in the past has had insufficient weatherability and, in part, due to an inability to protect finer textures from weathering, it has distorted objects viewed through it unless positioned within about 1" or less of the same.
Thus, problems in the past with transparent low glare thermoplastic sheet have been two-fold. Such sheet has had an insufficient level of weatherability and has tended to excessively distort objects viewed through it.
Therefore, it is an object of the present invention to produce a transparent low glare thermoplastic sheet having improved weatherability.
It is another object of the present invention to produce a transparent low glare thermoplastic sheet with reduced levels of distortion for objects viewed through it.
It is yet another object of the present invention to produce a transparent low glare sheet with a texture on at least one surface equivalent to that imprinted by a 10 microinch RMS roller and which textured surface has increased resistance to being obscured or destroyed by the effects of weathering.